Andrew Balcer, 19, entered the plea in an Augusta court Friday after being indicted on two counts of murder and another charge of animal cruelty.
Balcer was just shy of his 18th birthday on Halloween in 2016 when he allegedly stabbed his parents to death and also killed the family dog.
Prosecutors said he had been struggling with his gender identity and didn't feel like his parents would have supported him.
A court later ruled his case will be considered in adult court.
His trial is now scheduled for November.